This invention relates generally to a method and apparatus for applying an elastomeric handgrip to the handle of sporting goods such as a baseball or softball bat, tennis racquet, golf club, as well as to tools, implements, equipment, or other articles having an elongated handle segment, without the use of an installation fixture.
Many different types of handgrips are known for sporting goods, tools, implements, equipment, and other hand-held articles to increase the friction between the user's hand and the article, to provide protection or cushioning, and to achieve a particular mechanical advantage when using the article.
Cloth, leather, rubber, and plastic handgrips are adhered or otherwise applied to these types of articles, with installation of the handgrip being accomplished by a variety of methods: the handgrip may be wrapped around the handle segment of the article; the article may be dipped in or coated with a liquid compound that dries or congeals; a hollow tubular section of handgrip may be distended and the handle section of the article inserted longitudinally into the handgrip using an installation fixture; a handgrip member may be manufactured as an integral unit and mounted on the article; the handgrip may be molded or formed unitary with the article itself.
The subject matter of the present invention relates more specifically to applying or affixing a handgrip to an article subsequent to the initial manufacturing process, such as when replacing worn or inferior grips with new or preferred grips, adding a secondary grip with different physical characteristics in order to enhance the cushioning or gripping properties of the original, or mounting a grip on an article originally manufactured without any handgrip.
Elastomeric handgrips fabricated from rubber or plastic with either a smooth or serrated gripping surface are currently the preferred choice for baseball and softball bats, tennis and racquetball racquets, golf clubs, and other sporting goods. Using a baseball or softball bat as a representative example, two particular methods are most frequently utilized commercially for applying an elastomeric handgrip to the handle segment of such an article.
In the first method, a tubular grip having a closed end is placed within a vacuum chamber similarly having an open end, and the open end of the tubular grip is sealed around the open end of the chamber. Negative pressure is drawn between the chamber and the tubular grip, thus causing the tubular grip to expand or distend. The handle of the bat or other article is then inserted into the open end of the tubular grip, and the pressure within the chamber is equalized with the normal air pressure. The tubular grip contracts over the handle segment of the article, and any excess portion of the grip material is then cut away from the handle segment using a suitable cutting instrument. Such a method is disclosed in U.S. Pat. Nos. 4,016,640 and 4,134,198 to Briggs, and the vacuum system and grips are currently marketed by `totes` Incorporated of Loveland, Ohio.
The type of grips which may be applied using this process are limited to thin rubber materials having a relatively low elastic modulus due to the weak negative pressure that may be drawn using an electric motor driven vacuum pump. It is also necessary to cut away the excess material from the open end, and often the enclosed end of the tubular grip, which frequently results in an unfinished and aesthetically unsuitable appearance. Besides stocking the line of handgrips themselves, it is also necessary for a typical sporting goods store or pro shop to keep the equipment accessible in a predetermined area, maintain the motor and vacuum system in a safe and proper working condition, and staff the facility with trained operators.
In the second method, a tubular grip having two open ends is placed on an installation fixture, usually having a plurality of longitudinal tines that may flex radially outward and separate from one another. The length of the fixture is sufficient that if the tubular grip surrounds and constrains the tines at one end, the opposing ends of the tines may be manually separated so that the end of the bat or article may be received within or between those tines. The article is then forced further into the fixture, with the pressure exerted radially outward by the article on the tines being used to stretch and expand the tubular grip. Once the tubular grip is positioned circumscribing the desired portion of the handle segment, the fixture is removed from between the article and the tubular grip. Representative examples of this method and the associated installation fixtures are disclosed in U.S. Pat. Nos. 2, 038,840 to Hall and 4,466,166 to Hogarth.
Such a system permits thicker grips with a higher elastic modulus to be applied to such articles as softball or baseball bats when using a fixture supported by a tripod, however the force required must usually be exerted using a person's body weight or a levering device. Such an installation fixture, tripod, lever device, and grips are currently marketed by Tacki-mac.RTM. Grips, Inc. of Canoga Park, Calif. for use with baseball and softball bats and racquetball racquets. Removing the fixture may also present problems, such as interfering with the proper placement of the handgrip on the desired portion of the handle segment, or damaging the grip material or surface of the article.
A variation on this method utilizes a grip that is initially turned inside-out on one or more sleeves and lubricated, or folded repeatedly in discrete segments, as disclosed in U.S. Pat. Nos. 4,506,430 to Guzay; 4,685,189 to Palmqvist; and 4,912,836 to Avetoom.
These systems have proven workable for some applications involving relatively thin articles with uniform non-tapered cross-sections, such as golf club handles and high tension cables, but are not deemed suitable for larger applications such as baseball and softball bats, and would only be suitable for tennis or racquetball racquets and the like if the material is extremely thin. Removal of the sleeve can require more force or pull than can be accomplished manually, and the process can be time consuming. In addition, removal of the sleeve is problematical, particularly where the handle segment has a knob-shaped end, or where the handgrip is preferably or necessarily installed from the proximal as opposed to the distal end of a tapered article.
U.S. Pat. No. 4,185,375 to Brown discloses a method of applying a tubular elastomeric handgrip to articles such as sporting goods in which the handgrip is rolled into a spiral toroid and disposed on a hollow rigid cylindrical core from which the handgrip may be unrolled onto the handle segment. A plurality of handgrips may be positioned sequentially on the core. The handgrips are rolled using a forming mandrel having a thin cylindrical section joined to a thicker cylindrical section having a diameter equal to the core by a flared intermediate section which stretches the rolled handgrip to the appropriate size.
This system is only practical for use with handgrips having a very thin thickness or a very short length, since rolling the handgrip into a spiral toroid increases the compression ratio and force needed to expand the diameter of the toroid by many times. This process can also be destructive to the handgrip material itself, since the rolling process causes extreme lateral and axial deformation of the material within each spiral loop, and the shelf life of a rolled handgrip is therefore reduced significantly. It is also difficult and expensive to automate the rolling process and maintain uniformity.